To date, many attempts have been made in the art to improve the stain resistance of scoured carpets. Some approaches have involved treating the carpet with polycarboxylic acids and their conjugate bases. Thus, U.S. Pat. No. 4,937,123 (Chang et al.) describes a method for imparting stain resistance against acid colorants to polyamide fibers. In accordance with the method, the fibers are treated with an aqueous solution comprising polymethacrylic acid and copolymers thereof.
U.S. Pat. No. 5,346,726 (Pechhold) describes a polyamide fibrous substrate having deposited on it a stain resistant composition comprising a water soluble maleic anhydride/allyl ether or vinyl ether polymer.
U.S. Pat. No. 5,001,004 (Fitzgerald et al.) discloses the use of aqueous solutions of hydrolyzed ethylenically unsaturated aromatic/maleic anhydride polymers in the treatment of textiles to render them resistant to staining. Particular mention is made of the use of ammonium hydroxide as the hydrolyzing agent, although the reference notes that, when this agent is used, it is necessary to maintain the hydrolyzed polymer at an elevated temperature for an extended period of time in order to obtain satisfactory stainblocking properties on polyamide substrates.
U.S. Pat. No. 5,401,554 (Armen) discloses a process for making stain resistant melt colored carpet. In accordance with the method, a polyamide copolymer containing sulfonate groups is melt mixed with a coloring agent to form a homogenous polymer melt. The melt is spun into fibers which are tufted into a backing to form a carpet. The carpet is then treated with a compound which may be polymethacrylic acid or copolymers thereof, mixtures of polymethacrylic acid with a sulfonated aromatic formaldehyde condensation product, or a reaction product of the polymerization or copolymerization of methacrylic acid in the presence of a sulfonated aromatic formaldehyde condensation product. U.S. Pat. No. 5,436,049 (Hu) makes a similar disclosure except that, in the method described therein, the polyamide is melt mixed with a compound which is capable of reacting with the amino end groups of the polyamide so as to reduce the amino end group content thereof.
U.S. Pat. No. 3,835,071 (Allen et al.) discloses rug shampoo compositions comprising water soluble ammonium salts of styrene-maleic anhydride copolymers.
The treatment of scoured carpets with fluorochemical agents, to render them resistant to dry soil and repellent to water and oil-based stains, has been known in the art for many years. Successfully treated with these fluorochemical agents, fibrous materials, including carpets, textiles, leathers, and papers, resist the discoloration that results from normal soiling and staining and keep their original aesthetic appeal. For an overview of anti-soiling and anti-staining technology, see Mason Hayek, Waterproofing and Water/Oil Repellency, 24, Kirk-Othmer Encyclopedia of Chemical Technology, 448-55 (3d ed. 1979).
These fluorochemical agents are fluorochemical esters disclosed in U.S. Pat. No. 3,923,715 (Dettre), U.S. Pat. No. 4,029,585 (Dettre), and U.S. Pat. No. 4,264,484 (Patel) and fluorochemical urethanes and ureas disclosed in U.S. Pat. No. 3,398,182 (Guenthner et al.), U.S. Pat. No. 4,001,305 (Dear et al.) U.S. Pat. No. 4,792,354 (Matsuo et al.), and U.S. Pat. No. 5,410,073 (Kirchner). A number of other fluorochemical agents also used and described in the art include allophanate oligomers, biuret oligomers, carbodiimide oligomers, guanidine oligomers, oxazolidinone oligomers, and acrylate polymers. Commercial treatments of these various types are widely available and are sold, for example, under the "Scotchgard" and "Zonyl" trademarks.
Other attempts to improve the soil resistance of carpets have focused on the carpet manufacturing process itself. Both natural and synthetic carpet fibers contain oil residues on their surfaces at the time they are woven into the carpet. See, e.g., N. Nevrekar, B. Palan, "Spin Finishes for Synthetic Fibres--Part IV", Man-Made Textiles In India 331-336 (September 1991). These oil residues, which may be naturally occurring fats or waxes (in the case of wool and other natural fibers) or which may be residual spin finishes or other processing oils added during the manufacturing process (in the case of polypropylene and other synthetic fibers), significantly increase the tendency of the assembled carpet to attract dirt and other organic contaminants.
Consequently, it has become common practice in the art to "scour" carpets, a process which typically involves immersing the finished carpet in a bath of aqueous cleaning solution. The cleaning solution effectively reduces the amount of oil residue on the carpet to a level that does not significantly affect the soil resistance of the carpet. Indeed, it has long been considered essential that spin finishes be easily removable through scouring. See, P. Bajaj, R, Katre, "Spin Finishes", Colourage 17-26 (Nov. 16-30, 1987); W. Postman, "Spin Finishes Explained", Textile Research Journal, Vol. 50, No.7 444-453 (July 1980).
However, the immersion techniques involved in scouring carpets are undesirable in that they significantly increase the overall cost of manufacturing a carpet. After a carpet is scoured, it must be carefully dried in an oven or kiln to avoid warping or degradation of the carpet fibers. However, due to the immense effective surface area of a carpet, the carpet often absorbs many times its weight in water during scouring. Consequently, the drying process can be considerable, and consumes a significant amount of energy. This is especially true in the case of high quality carpets, which are usually denser than their lower quality counterparts. In the interim, the increased weight of the wetted carpets makes them very cumbersome to handle. Scouring also frequently induces static problems in the treated carpet.
There is thus a need in the art for a low wet pick-up method for imparting water and oil repellency to unscoured carpets, that is, carpets with spin-finish lubricants remaining on the fibers. In order to serve as a practical alternative to scoured carpets, carpets treated in accordance with such a method would have to exhibit soil resistance, water repellency, and/or oil repellency values comparable to, or better than, those exhibited by scoured carpets treated with similar materials.
Another problem in the art relates specifically to the use of ammonium salts of polycarboxylic acids in the treatment of carpets. To date, these materials have not found widespread acceptance as carpet treatment agents, largely because earlier work on these materials suggested that they required special handling procedures not necessitated by other carpet treatment agents. Thus, as noted previously, U.S. Pat. No. 5,001,004 (Fitzgerald et al.) teaches that it is necessary to maintain these materials at an elevated temperature for an extended period of time in order to obtain satisfactory stainblocking properties on polyamide substrates. Furthermore, these materials, like many other salts of polycarboxylic acids, were often found to exhibit poor shelf stability, rendering them undesirable for many practical applications. To date, the phenomena contributing to the poor shelf stability of salts of polycarboxylic acids, and in particular, the ammonium salts of these materials, has been poorly understood. There is thus a need in the art for salts of polycarboxylic acids, and in particular, ammonium salts of these materials, which have longer shelf lives.
These and other needs are met by the present invention, as hereinafter described.